Method for producing solid castings



No Drawing. Application December 4, 1952, Serial No. 324,124

Claims priority, application Sweden June 5, 1952 '2 Claims. (Cl. 22-215) The present invention relates to a new and improved method of producing ingots and castings so as to remove piping which may generally be said to result from the shrinking of the molten steel during the hardening, i. e. the chilling of the outer walls of the casting while its core and center is still molten, the molten core as it chills and and contracts shrinking away from the casting wall-s and leaving a pipe or cavity. As known said pipe occurs in the upper part of the casting and causes a considerable loss because that part of the casting where the pipe occurs is of inferior quality and must be cut away after the casting has been rolled.

Several difierent methods are proposed for removing said piping.

According to known methods it is proposed to deposit metal or slag-forming material on the top of the casting within the mold and then to add heat by electric energy and suitably arranged electrodes in order to melt the metal and fill the piping.

According to other known proposals it is endeavored to diminish the pipe by making the upper part of the casting narrower. For the same purpose and especially in order to raise the pipe to a level as high as possible in the casting it is endeavored to delay the chilling of its central part, for instance by arranging a heat insulating cover, i. e. a so called box around the upper part of the ingot mold, by adding heat to the upper part of the casting by electricity, direct heating or by adding a material such as thermit, which due to chemical reaction creates heat.

It is a common feature of all the last mentioned methods to diminish the piping that they are performed before solidification of the metal. Although rather good results are obtained by said known methods the piping is not entirely eliminated and it represented hitherto a still unsolved problem and severe drawback.

The present invention, however, gives a fully satisfactory solution, and it embodies a method by which the piping may be totally avoided.

According to this new method and contrary to the known methods the ingot or casting at first is allowed to solidify wholly in the mold. This results in the formation of a pipe within the upper part of the casting. After the States Patent Patented Aug. 14, 1956 solidification of the metal but preferably whilst it is still warm, a thermit mixture, known per se is applied on the top of the casting and brought into contact with its central part. The thermit ignites and immediately causes the central upper part of the casting to melt and to flow down and fill the pipe cavity. When the thermit has burnt, the molten metal will again chill and solidify. Due to the conducting of the heat, which mainly takes place downwards in the castmaterial the solidification will occur beginning at the lowest part of the filled piping and slowly ascend. When the solidification is finished the pipe cavity will be totally filled. No part of the later-on rolled ingot will have to be cut away. The slag from the reacting thermit compound will form an insulating cover on the upper surface of the casting contributing to the favourable result because the metal will solidify last at the top under said slag. The cold parts of the casting surrounding the remolten material filling the pipe cavity also aid in directing the chilling process in said material upwardly from below and to prevent a new pipe from forming.

According to another feature of the invention the amount of thermit is enough not only to melt the metal over the pipe but simultaneously to superheat it. Due to this, even a part of the inner-surface of the pipe will melt. This gives a good contact between the metal which flows down into the pipe cavity, and previously solidified parts ofthe casting. Oxides which may be present within the pipe will melt and flow up to the upper surface of the casting.

The manner in which the thermit compound is applied and ignited on the solidified casting top may of course be appropriately varied without departing from the scope of the invention. It may also be appropriate to provide the casting mold with an insulating cover.

What I claim is:

1. A method of producing pipeless steel ingots comprising the steps of casting molten steel in a mold, cooling the ingot to solidify it, applying a thermit to the top of the ingot after the pipe is formed therein and when the casting is still warm whereby the chemical reaction of the thermit produces a temperature higher than the melting temperature of the casting, the amount of said thermit being sufiicient after ignition to bring the upper part of the casting around the pipe cavity into the molten condition to melt and flow down and fill the pipe, whereafter the casting is allowed to chill and solidify again.

2. A method as described in claim 1 which said thermit superheats a part of the casting metal over and surrounding the pipe.

References Cited in the file of this patent UNITED STATES PATENTS 1,294,209 Walker Feb. 11, 1919 2,495,273 Lutts Jan. 24, 1950 2,513,602 Udy July 4, 1950 2,514,793 Pletsch et al. July 11, 1950 

1. A METHOD OF PRODUCING PIPELESS STEEL INGOTS COMPRISING THE STEPS OF CASTING MOLTEN STEEL IN A MOLD, COOLING THE INGOT TO SOLIDIFY IT, APPLYING A THERMIT TO THE TOP OF THE INGOT AFTER THE PIPE IS FORMED THEREIN AND WHEN THE CASTING IS STILL WARM WHEREBY THE CHEMICAL REACTION OF THE THERMIT PRODUCES A TEMPERATURE HIGHER THAN THE MELTING TEMPERATURE OF THE CASTING, THE AMOUNT OF SAID THERMIT BEING SUFFICIENT AFTER IGNITION TO BRING THE UPPER PART TO THE CASTING AROUND THE PIPE CAVITY INTO THE MOLTEN CONDITION TO MELT AND FLOW DOWN AND FILL THE PIPE, WHEREAFTER THE CASTING IS ALLOWED TO CHILL AND SOLIDIFY AGAIN. 